Single source DNA profile recovery from single cells isolated from skin and fabric from touch DNA mixtures in mock physical assaults

The ability to obtain DNA profiles from trace biological evidence is routinely demonstrated with so-called ‘touch DNA evidence’, which is generally perceived to be the result of DNA obtained from shed skin cells transferred from a donor's hands to an object or person during direct physical contact. Current methods for the recovery of trace DNA employ swabs or adhesive tape to sample an area of interest. While of practical utility, such ‘blind-swabbing’ approaches will necessarily co-sample cellular material from the different individuals whose cells are present on the item, even though the individuals' cells are principally located in topographically dispersed, but distinct, locations on the item. Thus the act of swabbing itself artifactually creates some of the DNA mixtures encountered in touch DNA samples. In some instances involving transient contact between an assailant and victim, the victim's DNA may be found in such significant excess as to preclude the detection and typing of the perpetrator's DNA. In order to circumvent the challenges with standard recovery and analysis methods for touch DNA evidence, we reported previously the development of a ‘smart analysis’ single cell recovery and DNA analysis method that results in enhanced genetic analysis of touch DNA evidence. Here we use the smart single cell analysis method to recover probative single source profiles from individual and agglomerated cells from various touched objects and clothing items belonging to known donors. We then use the same approach for the detection of single source male donor DNA in simulated physical contact/assault mixture samples (i.e. male ‘assailant’ grabbing the wrist, neck or clothing from the female ‘victim’, or being in transient contact with bedding from the ‘victim’). DNA profiles attributable to the male or female known donors were obtained from 31% and 35% of the single and agglomerated bio-particles (putative cells) tested. The known male donor ‘assailant’ DNA profile was identified in the cell sampling from every mixture type tested. The results of this work demonstrate the efficacy of an alternative strategy to recover single source perpetrator DNA profiles in physical contact/assault cases involving trace perpetrator/victim cellular admixtures.     

Reduce optimisation time and effort: Taguchi experimental design methods

Development and validation of new methods and technologies frequently require long periods of time and high costs to determine the optimal system. A commonly used approach to optimisation is the factorial method, where each variable is tested at every level of the other variables. An alternative approach is to modify the experimental design using a multifactorial approach. The Taguchi design method utilises orthogonal arrays, which distribute the variables in a balanced manner, thus greatly reducing the number of experiments required. We applied the Taguchi experimental design method to PCR optimisation, and significantly reduced the number of reactions required to create highly successful reactions. We found the Taguchi design method a valuable tool for the optimisation of multifactor experiments.     

Actuarial status of the OASI (old age survivors insurance) and DI (disability insurance) Trust Funds

This article summarizes the current financial condition and actuarial status of the Old-Age, Survivors, and Disability Insurance (OASDI) program, as shown in the 1987 Annual Report of the Board of Trustees. The Trustees note that the assets of the OASI and DI Trust Funds, on a combined basis, will be sufficient to permit the timely payment of OASDI benefits for many years into the future, on the basis of all four sets of assumptions shown in the report. For the next 75 years, the estimates show that the OASDI program, overall, is in close actuarial balance, based on the two intermediate sets of assumptions. The DI program by itself, however, is not in close actuarial balance for the next 75 years. The actuarial deficit for the DI program could be remedied by a small reallocation of the contribution rate from OASI to DI, in such a way that the OASI program would remain in close actuarial balance and OASDI benefits would not be affected. Although the Trustees are not recommending such a reallocation, they note that the financial condition of the DI program will need to be carefully monitored.     

Actuarial status of the OASI and DI Trust Funds

This article summarizes the current financial and actuarial status of the old-age, survivors, and disability insurance (OASDI) program, as shown in the 1985 Annual Report of the Board of Trustees. The Trustees note that the combined assets of the OASI and DI programs will be sufficient to pay OASDI benefits on time well into the next century based on all four sets of economic and demographic assumptions. Based on the pessimistic assumptions, the DI program could become unable to pay benefits on time by the end of 1987, but this problem could be prevented by a reallocation of contribution rates between the OASI and DI programs. For the long range--the next 75 years--the Trustees estimate that the OASDI program is in close actuarial balance based on intermediate assumptions--that is, the average annual income rate is estimated to be between 95 percent and 105 percent of the average annual cost rate during that period. The long-range actuarial deficit based on the intermediate (Alternative II-B) assumptions represents about 3 percent of the average annual cost rate for the program.